gms | German Medical Science

Objectives/Interrogation: Extension block pinning consists of a dorsal extension block K-wire and a second volar K-wire to hold the DIJ in extension. This technique has been modified by several authors to improve the accuracy of reduction and stability of fixation. However, dorsal fragments that are large, markedly displaced, or rotated are not easily controlled with a single extension block K-wire. In many cases, this is due to rotation of the dorsal fragment in the axial plane. To address these limitations, we previously proposed a modified procedure, the two extension block K-wire technique. An anatomic reduction is more easily obtained with two extension block K-wires. Together, the wires create a broader stabilizing force that prevents rotation of the dorsal fragment in the axial plane when a reduction force is applied. The parallel and lower angled wires contact a wide area of the fragment, and the fragment is strongly compressed when the distal phalanx in extended. However, there are limitations to this technique in certain circumstances. While two extension block wires can prevent the dorsal fragment from migrating proximally and rotating in the axial plane, they cannot exert sufficient compressive force against the distal part of the dorsal fragment. This results in dorsal rotation of the dorsal fragment in the sagittal plane. The goal of the study was to describe the results of a supplemental method to achieve anatomical reduction in cases that are insufficiently treated by the two extension block K-wire technique.

Methods: Of 95 displaced mallet finger fractures treated using a modified two extension block Kirschner-wire (K-wire) technique, 18 (19%) were found to have an irreducible dorsal fragment and distal interphalangeal joint (DIJ) incongruence, due to rotation of the dorsal fragment in the sagittal plane. In these cases, we additionally employed a dorsal counterforce technique to supplement the two extension block technique. An additional K-wire was used to apply counterforce against the distal part of the dorsal fragment and control rotation in sagittal plane.

Results and Conclusions: All 18 fractures united. Congruent joint surfaces and anatomical reduction were seen in all cases. The mean active flexion of the DIJs was 83.8° (range, 79-88°) and the mean extension loss was 0.4° (range, 0-4°).

We believe that the dorsal counterforce technique effectively supplements the two-extension block K-wire technique and aids control of dorsal fragment rotation in the sagittal plane.